The present invention relates to a cooling system. More particularly, the invention is an improved cooling system for an outboard motor having a water propulsion device powered by an internal combustion engine.
As is well known, outboard motors for use in powering watercraft include an engine powering a water propulsion apparatus of the motor, such as a propeller. These outboard motors have a cowling, which encloses the engine.
The motor is generally movably mounted to a stern of a watercraft, and as such, it is desirable that the motor be compact in dimension. Keeping the motor compact reduces air drag and reduces the force necessary to turn or trim the motor. In order that the outboard motor be small in dimension, the engine is arranged to be as compact as possible, and the cowling is sized to fit just around the engine.
The positioning of the engine in the small space defined by the cowling is beneficial when considering the above-stated goals, but creates several problems. A main problem is that the cowling traps significant heat generated by the engine.
Therefore, it has been a common practice to provide cooling for at least some or all of the exhaust system in addition to the cooling for the cylinders. Various arrangements have been proposed for communicating these cooling systems with each other but a particular problem arises in that the coolant for the outboard motor is generally taken directly from the body of water in which the watercraft is operating. Thus, the question of thermal shock is particularly important, principally in connection with the cooling of the cylinder block and cylinder head.
Arrangements have been provided for providing various types of flow patterns through the engine and its exhaust system but these have not been totally successful in meeting the diverse needs of these two parts of the engine.
It is, therefore, a principal object of this invention to provide an improved cooling system for an outboard motor engine wherein the exhaust and engine cylinder cooling are controlled so that the, needs of each can be more accurately controlled.
It is a further object of this invention to provide an improved flow control arrangement for such a diverse cooling system for an outboard motor.
An improved cooling system for an outboard motor having a water propulsion device powered by an internal combustion engine is desired.
In accordance with the present invention, there is provided a cooling system for an outboard motor. Preferably, the motor is of the type, which has a powerhead comprising an internal combustion positioned in a cowling. The motor includes a water propulsion device which is powered by the engine. The engine has an engine body assembly defining at least one cylinder. An induction system delivers at least an air charge to the cylinder and an exhaust system discharges a burnt charge from the cylinder to the atmosphere. The engine further comprises an output shaft arranged to drive the water propulsion device. The cooling system including a coolant delivery mechanism driven by the engine for drawing water from a body of water in which the outboard motor is operating and returning the drawn water back to the body of water. The cooling system comprises a first cooling path for cooling the cylinder and a second cooling paths for cooling the exhaust. The delivery mechanism is arranged to deliver coolant through the second cooling path and to a coolant drain. The delivery mechanism is also arranged to deliver coolant through the first cooling path to the coolant drain. Means control the flow of coolant from the engine through the first and second paths comprising first and second control valves disposed at respective downstream ends of the first and said second cooling paths for controlling the respective flow therethrough.
Further objects, features, and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings, which follows, when considered with the attached figures.